# Periodic Patterns Unit 4 – Periodic Table.

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Periodic Patterns Unit 4 – Periodic Table

Lesson Essential Question:
What patterns exist on the periodic table?

METALLIC TREND INCREASES INCREASES

ATOMIC RADIUS Radius is the distance from the center of the nucleus to the “edge” of the electron cloud. Atomic radii are usually measured in picometers (pm) or angstroms (Å). An angstrom is 1 x m.

ATOMIC RADIUS Since a cloud’s edge is difficult to define, scientists use define covalent radius, or half the distance between the nuclei of 2 bonded atoms. BROMINE = Br2 2.86 Å 1.43 Å 1.43 Å

DOWN A FAMILY OR GROUP WHY? INCREASES As you go down a family the n value increases making the radius larger.

ACROSS A PERIOD WHY? As you go across a period the number of protons increases, (nuclear charge) pulling the electrons in tighter making the radius smaller.

IONS - remember Metals Nonmetals Lose electrons becoming positive.
Calcium – Ca [Ar]4s2 Loses 4s2 e-s becoming Ca+2 and [Ar] Noble gas Configuration (Octet Rule) Nonmetals Gain electrons becoming negative. Chlorine – Cl [Ne]3s23p5 Gains one e- becoming Cl-1 and [Ar] Noble gas configuration. (Octet Rule)

IONS – How can I remember?
Metals Nonmetals This is Cat-ion - CATION This is Ann ion - ANION He is a “plussy” cat! She is unhappy and negative.

DOWN A FAMILY OR GROUP WHY? INCREASES As you go down a family the n value increases making the radius larger.

IONIC RADII TRENDS DECREASES then INCREASE ACROSS A PERIOD WHY? For the metals the nuclear charge is greater than then number of electrons pulling them in tighter making the radius smaller. At the nonmetals the radius gets larger because the ion has gained electrons.

METALLIC ATOM AND ION COMPARISON

NONMETALLIC ATOM AND ION COMPARISON
Why do the Noble Gases not have an ionic Radius?

ATOM AND ION COMPARISON
Why does Hydrogen not have an ionic Radius?

Shielding Effect As more electrons are added to atoms, the inner layers of electrons shield the outer electrons from the nucleus. The effective nuclear charge on those outer electrons is less, and so the outer electrons are less tightly held

Example of Shielding Effect

Ionization Energy The energy required to remove an electron from an atom is ionization energy. (measured in kilojoules, kJ)

IONIZATION ENERGY The larger the atom is, the easier its electrons are to remove. Ionization energy and atomic radius are inversely proportional. Ionization energy is always endothermic, that is energy is added to the atom to remove the electron.

IONIZATION TREND INCREASES INCREASES

Electron Affinity is a measure of the energy change when an electron is added to a neutral atom to form a negative ion

ELECTRON AFFINITY Why do the Alkaline Earth Metals and Noble Gases not have measurable Electron Affinities?

Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.

ELECTRONEGATIVITY

In Summary…. Electronegativity Electronegativity